Conventionally, in designing knitted fabrics of kitted products, methods of representation for making knitted fabrics such as knitting stitch symbols or knitting symbols defined by, for example, JIS L 0200 of the Japanese Industrial Standard, are used. The knitting stitch symbols are symbols indicating textures of various knitting stitches such as front knitting stitches, back knitting stitches, front tuck knitting stitches, back tuck knitting stitches, float stitches and transfer stitches. The knitting symbols are symbols indicating the order of knitting with a needle corresponding to each knitting stitch symbol. The methods of representation for making knitted fabrics designate individual knitting stitch constituting a knitted fabric, and according to this designation, knitting data for making a knitted fabric with an automatic flat knitting machine can be generated.
The applicant has proposed in Japanese Unexamined Patent Publication JP-A 60-71748 (1985) a technique for generating knitting data for an automatic flat knitting machine with color codes represented that are substituted for the knitting stitch symbols. Substituting color codes for the knitting stitch symbols makes it easy to design a knitted fabric by image processing with a computer, and textures of more kinds of knitting stitches can be displayed on displaying means, using a large number of colors.
The applicant also has proposed in Japanese Unexamined Patent Publication JP-A 7-70890 (1995) a technique for generating loop images of knitting stitches constituting a knitted fabric by simulation, utilizing data for making a knitted fabric, and displaying the simulated images of the knitted fabric. In this technique, image processing is performed in the following manner. Image data of knitting yarns is stored as yarn samples in advance, and the shape and the position of each loop of knitting stitches, the brightness of each portion and the like are determined based on data for making a knitted fabric, and the loop is divided into a plurality of segments, and synthesized as a loop corresponding to segmented image data of the yarn samples. The segmented image data determine the shape of each loop or the overlap with an underlying loop based on the data for making a knitted fabric. Spline approximation of the segmented image data of a knitting yarn is performed in accordance with the loop shape, and for the overlap with an underlying loop, a mask is produced and an exposed portion of the underlying loop is left, so that the knitted fabric is simulated with images. When the periphery of the yarn sample is made rough, fluffiness can be expressed. When an oblique line is added on the yarn sample, yarn twist can be expressed.
In the case of performing knit design, when the methods of representation for making a knitted fabric are used, the displayed images do not necessarily reflect faithfully the appearance of the actual knitted fabric that is knitted according to the data for making a knitted fabric. Therefore, a designer who designs a knitted fabric with data for making a knitted fabric has to have an ability of imagining the appearance of the actual knitted fabric in designing, and the knitted fabric cannot be designed intuitionally.
When the simulation of a knitting stitch loop proposed in JP-A 7-70890 is used, it is possible to design an actual knitted fabric intuitionally. However, the representation of the fluffiness in the periphery of a knitting yarn or the knitting yarn twist is artificial, and it is difficult to make it close to the feeling of the knitted fabric made by the actual knitting yarn. In particular, in the spline approximation of segments, when segments are simply joined in a curved section, an edge is generated in a junction between the segments, and if both ends of the segments are made soft and overlapped, smooth joining can be realized. However, such joining does not guarantee that fluffiness across the divided segments is displayed as being continuous as it was, and even if image data of a very fluffy knitting yarn is actually used as a color sample, it is difficult to represent natural feeling of the knitted fabric with images in which the knitted fabric is simulated.